Hello there. Yes, the company has a requirement to make sure their drivers are properly licensed (and endorsed) for the vehicle they are employing him/her to drive. If the tank is part of the truck, technically a motor-truck vs a truck tractor, and it is 500 gallons or larger, then he does need the endorsement. Hope this helps. It's a very confusing area of law for sure!
Make little things count. Teach midgets math.